In recent years, in a 3rd Generation Partnership Project (3GPP) which is a mobile communication system standardization project, a technique of arranging small cells (a small cell base station) in a macro cell and increasing a system capacity through the small cells in order to respond to a rapidly increasing traffic demand is under review.
On the other hand, since a large number of small cell base stations are included in a radio access network, signaling from the radio access network to a core network (specifically, a mobility management apparatus) increases.
Therefore, there is a problem in that a processing load in the mobility management apparatus is increased due to a large number of small cell base stations. Particularly, when a user terminal performs a handover frequently, such a problem becomes remarkable (for example, see Non Patent Literature 1).